I do not understand kernel modules

Hello friends.
I am a FreeBSD newbie, I am going to ask you a question that I have not
been able to solve reading the manual. I am using 5.3 release. I have
compiled a custom kernel in my old pentium 75 MHz machine to include the
driver for my sound card. I added the following lines to the kernel
config file
device sound
device "snd_es137x"
and compiled the kernel perfectly. (long time.... ;-) )
But there is something that I do not understand well. When I look at the
contents of /boot/kernel/ directory, I found that there are kernel sound
modules *.ko for every sound card the kernel supports. Should not there
be my sound card module alone?
Does It mean that you have to compile all the stuff, even if you are
going to use only one kind of sound card?
Am I missing something?
Thanks in advance.
Ramiro.